This invention is directed to an improved flexible diffuser assembly that has particular application in the aeration of a sewage medium. A unique advantage hereof is the ability of the diffuser assembly to be retrofitted to existing aeration systems, specifically the porous ceramic dome, a commercial system sold under the name, SANITAIRE, a registered trademark of Water Pollution Control Corporation of Milwaukee, Wis.
For a number of years one of the methods of introducing air bubbles into a waste water treatment tank, for the express purpose of aerating the waste water, has been through the use of domed porous ceramic diffusers that emit fine bubbles, where such diffusers are secured to an air supply manifold along the bottom of a sewage treatment tank. While these diffusers have worked satisfactorily when new, over a period of time there is a tendency for them to become clogged and thus less efficient. In time the entire plant operation has to be closed down and the domed ceramic diffusers laboriously cleaned to thereby restore the porosity of the ceramic domes to a condition approaching that of new diffusers; a very labor intensive operation. The original design of these domed ceramic diffusers provided for their being bolted to a base plate that in turn had been permanently fixed to an air distribution pipe. This allowed the domed diffuser to be removed and cleaned, or replaced if one had become too clogged to restore, or replaced if one had become damaged. While this method of cleaning the domed diffusers has worked, the down-time for this type of maintenance has proven to be a detriment in the continuity of the operation of the waste water treatment plant.
U.S. Pat. No. 3,997,634, to the inventor of this invention, teaches a diffuser assembly that has gained commercial acceptance since its introduction. Briefly, such assembly comprises a base consisting of a T shaped member formed of "delrin", or similar material, having a central bore therethrough. It is through said bore that the aerating fluid, such as gas, passes for treatment of the surrounding fluid medium. Overlying and contiguous with an annular portion of the top of said T shaped member is a flexible cap or cover, i.e., neoprene or the like, which engages or wraps around the peripheral edge thereof. Plural through holes are provided in the annular portion to permit the release of gas from the diffuser into the treatment medium.
While such diffuser assembly represented a departure from existing treatment systems, it was limited to new construction and it could not be adapted to be retrofitted to existing systems, i.e. existing piping and support mechanism. Not only is the diffuser assembly of this invention, utilizing a flexible diffuser membrane, ideal for in-system replacement of the ceramic dome assembly, it offers comparable performance. That is, the assembly according to this invention will provide an improved oxygen transfer efficiency and pressure headloss without the need to constantly drain the sewage treatment tank to allow cleaning of the diffusers. This will save considerable maintenance costs and reduce the additional energy costs required to deliver air to the ceramic diffusers when they begin to clog.
The advantages hereof will become more apparent in the description which follows, particularly when read in conjunction with the accompanying drawings.